Welding gun having contact tip and method of operating same

ABSTRACT

A welding gun adapted to secure a contact tip within the welding gun without threading the contact tip and without the use of tools. The contact tip may be adapted to abut a surface of a first member disposed within the welding gun. The surface may be a surface of a gas diffuser. The surface may be adapted to abut the contact tip. The contact tip also may be adapted for abutment with a second member to urge the contact tip toward the first member. The second member may be a portion of a nozzle adapted to abut the contact tip to urge the contact tip toward the surface of the first member. A method of assembling a welding gun also is provided. The method may comprise disposing a contact tip between a first and a second member and capturing the contact tip between the first and second members.

FIELD OF THE INVENTION

The present invention relates generally to welding systems, andparticularly to a wire-feed welding gun having a tip to guide wirethrough a nozzle of a welding gun.

BACKGROUND OF THE INVENTION

Welding is a method of joining, or separating, metal objects. Arcwelding is a common type of welding. An arc welding system typically iscomprised of a power supply coupled by an electrical cable to a weldinggun housing an electrode. A ground cable is used to connect the metalobject to the power supply. When the electrode is placed against themetal object, the electrode in the welding handle completes anelectrical circuit between the power supply and the metal object,allowing electrical current to flow through the electrode and metalobject. The electrical current produces an arc between the electrode andthe metal object. The heat of the electric arc melts the metal object inthe region surrounding the electric arc. A filler material may be addedto the molten metal. For example, a wire may be placed against themolten portion of the object, melting the wire and allowing the moltenwire to merge with the molten object. Once the electrode is drawn awayfrom the metal object, the circuit is broken and the molten mass beginsto cool and solidify, forming a weld.

MIG (Metal Inert Gas) welding is one type of arc welding. MIG welding isalso referred to as “wire-feed” or GMAW (Gas Metal Arc Welding). In MIGwelding, a metal wire is used as the electrode. The wire is shielded byan inert gas and the metal wire acts as the filler for the weld. Theinert gas is used to shield the molten metal from outside contaminantsand gases that may react with the molten metal. Non-inert gases, such asCO₂, may also be used in MIG welding.

The wire and gas are coupled through a cable to a welding gun. A typicalwelding gun used in MIG welding and similar welding systems has a handleand a neck that extends from the handle. The wire and gas are directedthrough the neck towards a workpiece. The neck typically has a nozzleassembly that is secured to the neck to direct the flow of wire and gastowards the workpiece. The wire is directed through a contact tip housedwithin the nozzle assembly. The electrical current is coupled from thecable to the wire through the contact tip. In addition, the end of thenozzle assembly typically has a cone-shape to taper the flow of gas fromthe welding gun. A typical welding gun has a switch, or trigger, that iscoupled to the wire feeder. When the trigger is operated, wire is fedthrough the tip and gas is directed through the nozzle towards aworkpiece.

Contact tips require frequent replacement during operation of thewelding gun. Many contact tips are threaded into the welding gun.However, threadless contact tip designs also have been used. Forexample, threadless contact tip designs having a cam surface have beenused. The cam surface is adapted to bind the contact tip against astationary protrusion when the contact tip is rotated.

Unfortunately, there are a number of problems associated with existingthreadless contact tip designs. For example, the process of binding thecontact tip against the protrusion produces a bending stress in thecontact tip. In addition, variations in the distance between the contacttip and the exterior portion of the nozzle, known as the tip-nozzlerecess, occur with existing threadless contact tip designs. A consistenttip-recess distance is critical in certain welding applications,especially robotic welding systems. In addition, molten spatter from theweld may deposit on the end of the nozzle, eventually requiringreplacement of the nozzle. Consequently, nozzles having a nozzle bodyand a removable threaded end section have been developed. However, weldspatter may contaminate the threads or the threads may experiencegalling, requiring a tool, such as a wrench, to remove the threaded endsection from the nozzle body.

There exists then a need for a welding gun that utilizes a threadlesscontact tip design. Additionally, there is a need for a welding gun thatenables a contact tip to be installed and removed without the use oftools. Furthermore, there exists then a need for a welding gun thatutilizes a removable nozzle end section that may be secured and removedwithout threads or the use of tools. Finally, there exists a need for anozzle assembly having a threadless contact tip design that produces aconsistent tip-recess distance.

SUMMARY OF THE INVENTION

The present technique provides a welding gun adapted to secure a contacttip within a nozzle assembly without threading the contact tip andwithout the use of tools. The contact tip may be captured by abutmentbetween two members. The two members may be a gas diffuser and a portionof a nozzle.

In some embodiments of the present technique, a gas diffuser that isadapted to receive the contact tip in abutment is provided. The gasdiffuser may have a tapered surface adapted for sealing engagement witha tapered surface of the contact tip. Furthermore, in some embodimentsof the present technique, a nozzle adapted to abut a portion of thecontact tip. The nozzle may comprise an insert disposed within a nozzlebody. The nozzle may also be adapted for threaded engagement with thegas diffuser.

Another aspect of the present technique is a method of assembling anozzle assembly of a welding gun. The method may comprise disposing acontact tip between two members of the nozzle assembly. The method mayalso comprise securing the nozzle to the gas diffuser to capture thecontact tip between the gas diffuser and the nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings in which:

FIG. 1 is a diagram of a MIG welding system, according to an exemplaryembodiment of the present technique;

FIG. 2 is a front elevational view of a MIG welding gun, according to anexemplary embodiment of the present technique;

FIG. 3 is an exploded view of the nozzle assembly of the MIG welding gunof FIG. 2;

FIGS. 4 and 5 are cross-sectional views of the nozzle assembly,illustrating the assembly of the nozzle assembly, according to anexemplary embodiment of the present technique;

FIG. 6 is an end view of the nozzle assembly of FIG. 4;

FIG. 7 is a cross-sectional view of an alternate embodiment of a nozzleassembly, according to an exemplary embodiment of the present technique;

FIG. 8 is an exploded view of the alternate embodiment of a nozzleassembly; and

FIG. 9 is an embodiment of a retaining ring for securing the detachablecone to the nozzle, according to an exemplary embodiment of the presenttechnique.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring generally to FIG. 1, an exemplary metal inert gas (“MIG”)welding system 20 is illustrated. However, the present technique may beused in other wire feed welding systems, such as submerged arc welding.The illustrated MIG welding system 20 comprises a power source/wirefeeder 22, a gas cylinder 24 containing a gas 25, a spool 26 ofelectrode wire 27, a welding gun 28, a welding cable 30, a work clamp32, and a ground cable 34. In the illustrated embodiment, the gas 25 andwire 27 are routed from the power source/wire feeder 22 to the weldingcable 30. The welding cable 30, in turn, routes the gas 25 and the wire27 to the welding gun 28. The power source/wire feeder 22 also may becomprised of a separate power source and a separate wire feeder.

The welding cable 30 also has conductors (not shown) for conveying largeamounts of electric current from the power source/wire feeder 22 to thewelding gun 28. The power source/wire feeder 22 is operable to controlthe feeding of wire 27 to the welding gun 28. In addition, the powersource/wire feeder 22 also may be used to control the flow of gas 25 tothe welding gun 28. To assemble the system, a ground cable 32 having aclamp 34 is connected to the power source/wire feeder 22. The clamp 34is clamped onto a workpiece 36 to electrically couple the workpiece 36to the power source/wire feeder 22. The work clamp 32 and ground cable34 electrically couple the power source/feeder 22 to the workpiece 36.Additionally, the wire 27 within the MIG welding cable 30 may beelectrically coupled to the power source/wire feeder 22.

The welding gun 28 is used to direct the wire 27 towards the workpiece36. When the wire is touched to the workpiece 36, an electrical circuitbetween the workpiece 36 and power source/wire feeder 22 is completed.Electric current flows from the power source 22 through the weldingcable 30, the electrode wire 27, the workpiece 36, the workclamp 34, andthe ground cable 32 back to the power source 22. An arc is producedbetween the electrode wire 27 and the workpiece 36. The electric arcmelts the workpiece 36 in a region surrounding the arc, forming a weldpuddle. The heat of the arc melts the wire 27 along with the workpiece36, enabling the electrode wire 27 to act as-a filler material for theweld puddle. The inert gas 25 forms a shield that prevents harmfulchemical reactions from occurring at the weld puddle. When the arc isremoved, the weld puddle solidifies, forming the weld.

Referring generally to FIGS. 1 and 2, the welding gun 28 comprises ahandle 38, a trigger 40, a neck 42, and a nozzle assembly 44. The neck42 is secured to the handle 38 by a locking nut 46. The MIG weldingcable 30 also has an electrical cable (not shown) that is electricallycoupleable to the trigger 40. The trigger 40 enables a user to controlthe supply of electrode wire 27 and power from the power source/feeder22. A number of events occur when the trigger 40 is operated. One eventis that the power source/wire feeder 22 draws in wire 27 from the wirespool 26 and feeds it though the MIG welding cable 30 to the welding gun28. Also, electric power from the power source/feeder 22 is supplied tothe wire 27. The welding gun may be adapted to enable the flow of gas 25from the gas cylinder 24 to be controlled by the trigger 40. The wire 27and gas 25 are then fed through the neck assembly 42 towards theworkpiece 36. The nozzle assembly 44 directs the wire 27 and gas 25towards the target 36. When the trigger 40 is released, the wire 27 andelectric current are no longer fed to the welding gun 28.

Referring generally to FIG. 3, the nozzle assembly 44 comprises a gasdiffuser 48, a tip 50, and a nozzle 52. Gas 25 flows from the weldingcable 30 and the welding gun 28 to the gas diffuser 48. The gas diffuser48 is used to establish desired flow characteristics of the gas 25. Thenozzle 52 is used to direct the gas 25 from the gas diffuser 48 towardsthe workpiece 36. The tip 50 is used to direct the wire 27 from thewelding gun 28 and to conduct electric current from the welding cable 30to the electrode wire 27. The large amounts of electric current drawnfrom a typical power source/wire feeder 22 during welding could damagethe electrode wire 27 if the electric current was conducted through theentire length of the electrode wire. Therefore, the welding cable 30,rather than the electrode wire, is used to conduct most, if not all, ofthe electric current from the power source/wire feeder 22 to the weldinggun 28. The contact tip 50 is used to transfer the electric currentflowing through the welding cable 30 to the electrode wire 27. Thecontact tip 50 is electrically coupled to the welding cable 30 by theneck 42 and the gas diffuser 48.

In the illustrated embodiment, the contact tip 50 is secured within thewelding gun 28 by abutment with the gas diffuser 48 and nozzle 52,rather than by threading the tip 50 into the gas diffuser 48. Thecontact tip 50 has a channel 54 that extends through the length of thecontact tip 50 that is used to direct the electrode wire 27 through thecontact tip 50. In addition, the channel 54 is used to bring theelectrode wire 27 into contact with the contact tip 50 so that electriccurrent may be conducted from the contact tip 50 to the electrode wire27. In the illustrated embodiment, the channel 54 defines an axisextending linearly through the contact tip 50, the gas diffuser, and thenozzle 52. In addition, in this embodiment, the contact tip 50 issymmetrical about the axis.

As best illustrated in FIG. 4, the contact tip 50 has an end surface 56that is adapted to abut a seating surface 58 of the gas diffuser 48 anda shoulder 60 that extends around the contact tip 50 for engagement bythe nozzle 52. In the illustrated embodiment, the end surface 56 isuniform around the contact tip 50. Preferably, the end surface 56 of thecontact tip 50 and the seating surface 58 of the gas diffuser 48 areadapted for sealing engagement to prevent gas from escaping between thegas diffuser 48 and the contact tip 50. In the illustrated embodiment,the end surface 56 and the seating surface 58 are tapered to have agenerally conical shape. However, the end surface 56 and the seatingsurface 58 may be curved or otherwise configured for mutual abutmentand/or for sealing engagement. In the illustrated embodiment, theshoulder 60 protrudes from the contact tip 50 and is adapted to beabutted. In this embodiment, the shoulder 60 is uniform around thecontact tip 50.

In the illustrated embodiment, the nozzle 52 and the contact tip 50 aresecured to the welding gun when the nozzle 52 is secured to the gasdiffuser 48. The nozzle 52 has a nozzle body 62, a nozzle insert 64, anda layer of insulation material 66 disposed between the nozzle insert 64and the nozzle body 62. In the illustrated embodiment, the nozzle body62 has a conical portion 68 for directing the flow of gas 25 towards theworkpiece 36. The nozzle insert 64 has a threaded portion 70 that isadapted for threaded engagement with a threaded portion 72 of the gasdiffuser 48. In the illustrated embodiment, the nozzle insert 64 has anannular portion 74 that is adapted for engagement with the shoulder 60of the contact tip 50. The annular portion 74 has an opening 75therethrough for enabling the contact tip 50 to extend through thenozzle insert 64. The annular portion 74 may be a separate removablesecuring member, such as a retaining ring or snap ring.

Preferably, the shoulder 60 extends around the entire circumference ofthe contact tip 50 and is transverse to the axis of the contact tip 50so as to be in facing relationship with the annular portion of thenozzle insert 64. The contact tip may be adapted with other types ofprotrusion, other than the shoulder 60 illustrated in the figures. Forexample, the contact tip may be adapted with a plurality of separateprotrusions spaced at various locations around the circumference of thecontact tip. In addition, a securing member, such as a retaining ring orsnap ring, may be secured to the tip to act as a protrusion.

The contact tip 50 is disposed between the gas diffuser 48 and thenozzle 52 prior to securing the nozzle 52 to the gas diffuser 48.Because the illustrated embodiment is uniform about the axis of thecontact tip 50, the contact tip 50 may be disposed between the gasdiffuser 48 and nozzle 52 in any rotational orientation. As illustrated,there is a gap 76 between the annular portion 74 and the shoulder 60 ofthe contact tip 50. However, the contact tip 50 may be disposed throughthe nozzle insert 64 prior to disposing the contact tip 50 against thegas diffuser 48. Consequently, the gap 76 may be between the gasdiffuser 48 and the contact tip 50, rather than between the contact tip50 and the nozzle insert 64.

As best illustrated in FIG. 5, the nozzle 52 is drawn towards the gasdiffuser 48 as the nozzle 52 is threaded onto the gas diffuser 48, asrepresented by the arrow 77. The annular portion 74 of the nozzle insert64 abuts the shoulder 60 of the contact tip 50 and urges, or holds, thecontact tip 50 axially against the gas diffuser 48, bringing the endsurface 56 of the contact tip 50 into abutment with the seating surface58 of the gas diffuser 48 and thereby capturing the contact tip 50between the gas diffuser 48 and the nozzle 52. Preferably the annularportion 74 of the nozzle insert 64 extends around the inner portion ofthe nozzle 52.

Referring generally to FIGS. 4-6, gas 25 enters the gas diffuser 48 fromthe neck 42 via an entrance chamber 78. In the illustrated embodiment,the gas diffuser has a plurality of exit holes 79 for the gas 25 to exitthe gas diffuser 48. In addition, the annular portion 74 of the nozzle52 has a plurality of gas delivery holes 80. The gas delivery holes maybe round, or slots. The gas delivery holes 80 enable gas 25 to passthrough the annular portion 74 and enter the conical portion 68 of thenozzle 52. Contrary to previous nozzle embodiments, the gas deliveryholes 80 of the illustrated embodiment extend in parallel to the contacttip 50, thus improving the flow characteristics of the gas 25 flowingfrom the nozzle 52.

Referring generally to FIG. 7-9, an alternative embodiment of a nozzle82 is illustrated. In this embodiment, a detachable cone 84 is used. Thedetachable cone 84 is adapted to be secured to and removed from a nozzlebody 86 without the use of a tool. In the illustrated embodiment, thedetachable cone 84 comprises a conical portion 88, a cylindrical portion90, and an annular ring portion 92. The cylindrical portion 90 of thedetachable cone 84 is disposed within the interior of the nozzle body86. The annular ring 92 limits the travel of the detachable cone 84 intothe nozzle body 86. In the illustrated embodiment, the cylindricalportion 90 has an external groove 94 and the nozzle body 86 has acorresponding internal groove 96. However, the cylindrical portion 90and the nozzle body 86 may be adapted conversely, i.e., the cylindricalportion 90 may have an internal groove 96 and the nozzle body 86 mayhave the external groove 94. In addition, in this embodiment, a springretaining ring 98 is disposed within the external groove 94 of thedetachable cone 84 to secure the cone 84 to the nozzle body 86. However,other devices, such as a snap ring, may be used to secure the detachablecone 84 to the nozzle body 86.

In the illustrated embodiment, the cylindrical portion 90 of thedetachable cone 84 is pushed into the nozzle body 86 to secure the cone84 to the nozzle body 86. During installation of the cone 84, the ring98 is compressed as the cylindrical portion 90 of the cone 84 isinserted into the nozzle body 86. A user may compress the retaining ring98 or the ring 98 may be compressed by the nozzle body 86. When theretaining ring 98 reaches the internal groove 96 in the nozzle body 86,the retaining ring 98 expands outward into the internal groove 96. Inthe illustrated embodiment, retaining ring 98 occupies a portion of theinternal groove 94 of the cone 84 and the internal groove 96 of thenozzle body 86, thereby obstructing displacement of the cone 84 andnozzle body 86 and securing the cone 84 to the nozzle body 86.

In the illustrated embodiment, the retaining ring 98 is strong enough tosecure the cone 84 to the nozzle body 86, but may be overcome by a user.To remove the detachable cone 84 from the nozzle body 86, a user grabsthe cone 84 and pulls the cone 84 away from the nozzle body 88. Theannular ring portion 92 assists a user in gripping the detachable cone84. A new detachable cone 84 and/or retaining ring 98 may then besecured to the nozzle body 86. Thus, the detachable cone 84 may besecured to the nozzle 52 and removed without the use of tools.

The above embodiments provide a contact tip and a detachable cone thatare threadless. In addition, because the contact tip is secured bythreading the relatively large diameter nozzle to the gas diffuser,rather than the contact tip, no tools are needed to secure the contacttip to or remove the contact tip from the nozzle assembly. In addition,the cone may be secured to and removed from the nozzle without the useof tools. Furthermore, as best illustrated in FIGS. 5 and 7, theembodiments provided above enable the tip-nozzle recess 100 between theend 102 of the tip 50 and the exit opening 104 of the conical portion 88of the nozzle 52 to be consistent as contact tips and conical portionsof the nozzle are replaced.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown in the drawingsand have been described in detail herein by way of example only.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1-12. (canceled)
 13. A welding gun for an arc welding system,comprising: a first member; a second member disposed coaxially with thefirst member; and a contact tip disposable coaxially with the firstmember and the second member, wherein the contact tip is capturedbetween the first and second members.
 14. The welding gun as recited inclaim 13, wherein the contact tip comprises a symmetrical end surfaceadapted for axial abutment with the first member.
 15. The welding gun asrecited in claim 13, wherein the contact tip comprises a second surfaceadapted for abutment with the second member.
 16. The welding gun asrecited in claim 15, wherein the second surface comprises a shoulderextending around the contact tip.
 17. The welding gun as recited inclaim 13, wherein the second member is axially displaceable relative tothe first member to urge the contact tip toward the first member. 18.The welding gun as recited in claim 13, wherein the first membercomprises a gas diffuser.
 19. The welding gun as recited in claim 18,wherein the gas diffuser and the contact tip are adapted for sealingengagement.
 20. The welding gun as recited in claim 13, wherein thesecond member comprises a nozzle.
 21. The welding gun as recited inclaim 20, wherein the second member comprises an annular insert disposedwithin the nozzle.
 22. The welding gun as recited in claim 21, whereinthe annular insert comprises a plurality of gas delivery holes extendingtherethrough to enable gas to flow through the nozzle in parallel withthe contact tip.
 23. The welding gun as recited in claim 13, wherein thecontact tip is symmetrical about an axis through the contact tip.
 24. Awelding gun for an arc welding system, comprising: a first member; asecond member axially displaceable relative to the first member; and acontact tip disposed intermediate the first and second members, whereinthe contact tip is secured to the welding gun by abutment between thefirst member and the second member.
 25. The welding gun as recited inclaim 24, wherein the contact tip and the first member are adapted foraxial abutment.
 26. The welding gun as recited in claim 24, wherein thecontact tip and the second member are adapted for axial abutment. 27.The welding gun as recited in claim 24, comprising a third membersecured to the second member, the third member being adapted to abut thecontact tip.
 28. The welding gun as recited in claim 24, comprising afourth member secured to the contact tip, the fourth member beingadapted to abut the second member.
 29. The welding gun as recited inclaim 24, wherein the contact tip is threadless.
 30. The welding gun asrecited in claim 24, wherein the second member comprises a nozzleadapted for abutment with the contact tip.
 31. The welding gun asrecited in claim 24, wherein the first member comprises a gas diffuseradapted for abutment with the contact tip.
 32. A nozzle for a weldinggun, comprising: a first portion adapted for abutment with a contact tipto urge the contact tip towards a first surface located opposite thefirst portion.
 33. The nozzle as recited in claim 32, wherein the firstportion comprises an insert disposed within a nozzle body.
 34. Thenozzle as recited in claim 32, wherein the first portion comprises anannular surface adapted to receive a portion of the contact tiptherethrough.
 35. The nozzle as recited in claim 32, comprising a secondportion adapted for threaded engagement to secure the nozzle to thewelding gun.
 36. A gas diffuser for a welding gun, comprising a surfaceadapted for abutment with a corresponding surface of a contact tip. 37.The gas diffuser as recited in claim 36, wherein the surface is adaptedfor sealing engagement with the corresponding surface of the contacttip.
 38. The gas diffuser as recited in claim 36, wherein the surface istapered.
 39. The gas diffuser as recited in claim 36, comprising athreaded portion adapted for threaded engagement with a correspondingthreaded portion of a nozzle.
 40. A method of assembling a welding gun,comprising the acts of: disposing a contact tip between a first membersecured to the welding gun and a second member securable to the weldinggun; and securing the second member to the welding gun to capture thecontact tip between the first member and the second member.
 41. Themethod as recited in claim 40, wherein disposing comprises inserting aportion of the contact tip through an annular portion of the secondmember.
 42. The method as recited in claim 40, wherein disposingcomprises disposing an end surface of the contact tip against acorresponding surface of the first member.
 43. The method as recited inclaim 40, wherein the second member comprises a nozzle and securingcomprises threading the nozzle onto the welding gun.
 44. A welding gunfor an arc welding system, comprising: a first member; a second member;and a contact tip disposed intermediate the first member and the secondmember, wherein the contact tip is captured between the first member andthe second member by reducing the axial displacement between the firstand second members.
 45. A welding system, comprising: a welding gunadapted to receive a wire from a wire feeder, the welding gun comprisinga first member; a second member; and a contact tip, wherein the firstmember, second member and contact tip are adapted to receive the wiretherethrough, the contact tip being captured by the first and secondmembers.
 46. The system as recited in claim 45, comprising the wirefeeder.
 47. The system as recited in claim 46, comprising a power supplycoupled to the wire feeder to provide electric current to the wire. 48.The system as recited in claim 45, wherein the contact tip is abutted bythe first and second members.
 49. The system as recited in claim 48,wherein the first member is a gas diffuser.
 50. The system as recited inclaim 48, wherein the second member is a portion of a nozzle bodyassembly.